Merge "Add constants kDsuScratch and kDsuUserdata" am: 053df534d7 am: b465fe24cd am: 7a240ab7e7

Original change: https://android-review.googlesource.com/c/platform/system/gsid/+/1469542

Change-Id: I32d6aa9889aa39d165ce2ffdb119e7757882752b